Exercise devices utilizing fluid resistance devices are known to have numerous advantages over exercise devices utilizing springs or weights. For example, Cuinier, in U.S. Pat. No. 3,495,824, discloses exercise equipment in which resistance to the motion of a lever arm is generated by a fluid resistance device. The fluid resistance device of Cuinier's patent uses, as the force opposing muscular effort, the resistance produced by forcing a liquid through a constriction. Cuinier's fluid resistance device includes a fluid filled cylinder having a shaft centered therein. A lever in Cuinier's device is connected to the shaft in the cylinder, and the shaft is connected to a piston for driving liquid through a constriction. Movement of the piston in either direction forces fluid out of the cylinder and into an external conduit containing a constricting element; by use of a branched conduit system and one way valves, fluid resistance can be varied depending on the direction in which the piston is moved in the cylinder and depending on the fluid flow rate. In order to adjust the resistance to flow, Cuinier's device is provided with adjustable needle valves in the external conduits.
U.S. Pat. No. 4,854,577, to Simms, discloses an exercise machine having a double-acting hydraulic pump in which the resistance to movement in opposite directions can be varied. Simms utilizes a complicated conduit and valve system, which includes two non-return valves as well as two pressure valves having adjustable spring loaded plungers. The patents discussed above, and all other references mentioned herein, are incorporated by reference as if reproduced in full below.
Construction of prior art fluid resistance exercise devices, such as those disclosed in the Cuinier and Simms patents, is complicated due to use of elaborate conduit and valve systems. The inclusion of needle valves, which merely constrict flow through a conduit, allow the user to operate the prior art exercise equipment with minimal effort, thus reducing the benefits of using the exercise device; this is because the amount of resistance will depend on the speed at which the user wishes to move the fluid or operate the user driven lever (or levers) connected to the fluid resistance device. Hence, a consistent exercise program is difficult to accomplish using such a design because the user has no obligation to exert a minimum amount of pressure on each stroke in order to move the fluid from one portion of the device to the other through the constriction valve. In contrast, an athlete attempting to utilize exercise equipment having solid weights or springs must exert a minimum force to lift the weights or extend a spring; failure to exert a sufficient force will prevent the athlete from completing the exercise since the weight or spring will not move. In other words, there is an all or nothing response in conventional exercise equipment utilizing weights or springs which is not duplicated in prior art fluid resistance devices.
In devices, such as that disclosed in the Simms patent, which utilize non-return valves that are dependent on gravity, the device must always be used in an up-right position (i.e., correct operation of the fluid resistance device is orientation dependent). It is especially important that exercise devices to be utilized by astronauts in space not be dependent on their orientation for correct operation due to the low gravitational forces in the spacecraft; hence, conventional exercise equipment utilizing weights is too bulky and heavy to send into space, and would be of no use in a gravity free (weightless) environment. Further, spring operated exercise equipment can be dangerous when used in close proximity to other humans or in small compartments, such as spacecraft compartments.
Thus, there is a need for a simplified fluid resistance device for use in exercise systems, in which resistance to motion in opposite directions can be adjusted, and in which a minimum pressure must be applied in order to induce fluid flow within the device. There is also a need for a fluid resistance device which can operate in an orientation and/or gravity free environment.
Therefore, it is a primary object of the present invention to provide a simplified push pull exercise system utilizing a fluid resistance device, having no external fluid flow conduits.
It is a further object of the present invention to provide an improved simplified push pull exercise system utilizing a fluid flow resistance device having unitary one way flow valves which provide for an adjustable minimum flow resistance.
It is yet another object of the present invention to provide a fluid flow resistance device which can be used in any orientation.